We have identified first degree relatives of individuals with IDDM who have islet cell antibodies (RPN #94-01-25-06). Those individuals who screened positive were invited to undergo "staging" which consists of confirmation of ICA status, measurement of insulin autoantibodies (IAA), determination of HLA status, an intravenous glucose tolerance test (IVGTT) on two separate occasions at least three weeks apart, and an oral glucose tolerance test (RPN #94-10-17-01). The overall goal of this nationwide study is to determine if parenteral insulin or oral insulin can prevent or delay the onset of insulin-dependent diabetes in individuals at high risk for developing IDDM. The aim of this study is to study the effect of oral insulin in preventing or delaying the onset of insulin-dependent diabetes in individuals who have a 25-50% risk for developing IDDM in the next five years. The experimental group will be given active orally-ingested recombinant human insulin daily in the form of a capsule or sprinkled on food. The dose will be 7.5 mg/day as single daily dose one-half hour before breakfast. The rationale for this intervention is that the intestinal mucosa could induce disease relevant immunological tolerance to the presentation of an islet cell autoantigen (i.e., oral insulin), thereby delaying the development of IDDM. There will be a placebo group in this part of the study.